RE: Query started getting 1722 error - interesting explanation wh y

Hmm, I think I checked that at the time but a week and a half later I can't
say for certain. Currently that is not the case but currently it's back to
the old explain plan as well so that doesn't say anything.

I got a call from a developer the other week complaining that a query in QA
had started giving an ora-1722. It had worked fine for several months and
the identical query was working fine in production.

Select count(1)

from prod.job_profile jp

where step_id < 9999

and not exists (select 'x' from prod.job_log jl

where jl.job_id = jp.job_id
and ( jl.status in ('C', 'EI') )
and jl.batch_id in (select to_number(text_value)
from prod.batch_parameter
where name = 'BATCH_ID'));

Investigating confirmed this, along with the fact that the query was
comparing a string (jl.batch_id) with a number (to_number(text_value)). But
why did it suddenly stop working and why did it still work in production?

Comparing explain plans between QA and production I saw that they were
different (statistics had changed during QA testing). The query that failed
was using an index on jl.batch_id.

Apparently Oracle automatically took care of converting the string to a
number *unless* the number was being used to access an index on the varchar2
column. Interesting behavior. I can see why it might work that way but
it's certainly not intuitive.

Of course explaining this to the developer took quite a while. "It worked
before, why shouldn't it work now? What's wrong with Oracle?"

Oracle 9.2.0.6

Jay Miller

Sr. Oracle DBA

.

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